How to call the code behind return type function in javascript

[krishna]

Pls tell me how get the return type function value in javascript.below i m providing my code.

.Js File Code

tooltip_text = function(start, end, event) {     
      var FF = EHR.GetPhysicianName("Test");
    return FF;
};

.Cs File 

[DirectMethod]
        public static string GetPhysicianName(string PHYID)
        {            
            return "Hello"+ PHYID;
        }

pls help me as soon as possible....